The structural characteristics determined in our initial studies tend to place the Molluscum contagiosum virus (MCV) genome among other members of the poxvirus group in terms of genome molecular weight and organization. The apparent denaturability of the MCV genome into a continuous, single-stranded circle would point to the presence of terminal cross-links in the DNA molecule. So far, this structural arrangement appears to be unique to members of the poxvirus group. Furthermore, genome comparison studies of eleven independently isolated virus samples using techniques of electron microscopy and agarose gel electrophoresis revealed only three genetic types of MCV. The objective of these studies has been to define these structural features of the DNA molecules and to relate them to the biochemical events involved in the replication and growth of this virus in the cells they infect.